我正在为我的AP计算机科学课做一个java分数计算器，我的reduce方法有问题。我认为它只是返回作为简化答案输入的第一个分数。例如，4/5 * 5/4返回20/20而不使用reduce方法调用。这个答案是正确的，但是当我应用我的reduce方法时，它返回4/5（第一个分数）而不是1（或1/1）。任何反馈总是有用的。这是我的代码：
// begin fraction class.
public class Fraction {
// instance variables for the first fractions numerator and denominator.
private int numerator;
private int denominator;
public Fraction(String fraction) {
// This if statement checks for mixed numbers (indicated by the underscore)
if (fraction.contains("_")) {
// gets from 0 to before the first underscore is present to find the value of the whole number in the string.
int wholeNumber1 = Integer.parseInt(fraction.substring(0, fraction.indexOf("_")));
// does the same for numerator.
numerator = Integer.parseInt(fraction.substring(fraction.indexOf("_") + 1, fraction.indexOf("/")));
// does the same for denominator.
denominator = Integer.parseInt(fraction.substring(fraction.indexOf("/") + 1));
// sets mixed numbers into improper fractions
numerator = (wholeNumber1 * denominator) + numerator;
} else if (fraction.contains("/")) {
// this if statement checks for regular fractions.
// locates the numerator in the string.
numerator = Integer.parseInt(fraction.substring(0, fraction.indexOf("/")));
//locates the denominator in the string
denominator = Integer.parseInt(fraction.substring(fraction.indexOf("/") + 1));
} else {
// this else statement assumes that the user enters a whole number.
int wholeNumber2 = Integer.parseInt(fraction.substring(0));
numerator = wholeNumber2;
// puts the whole number over 1 to make an improper fraction. This will probably be reduced in another method.
denominator = 1;
}
} // end of Fraction constructor
// Starting methods for checkpoint 4+
public Fraction (int numerator, int denominator) {
// we used this.numerator and this.denominator to make it clear which variable is being referred to.
this.numerator = numerator;
this.denominator = denominator;
} // end of second Fraction constructor.
// method for formatting fractions.
public String toString() {
return String.valueOf(numerator) + "/" + String.valueOf(denominator);
}
// multiply method.
public Fraction multiply(Fraction secondFraction) {
int productOfNumerators = numerator * secondFraction.numerator;
int productOfDenominators = denominator * secondFraction.denominator;
// object to call the second constructor.
Fraction product = new Fraction(productOfNumerators, productOfDenominators);
return product;
} // end multiply method
// divide method.
public Fraction divide(Fraction secondFraction) {
// product of numerators and denominators for cross multiplication.
int productOfNumerators = numerator * secondFraction.denominator;
int productOfDenominators = denominator * secondFraction.numerator;
// object to call the second constructor.
Fraction quotient = new Fraction(productOfNumerators, productOfDenominators);
return quotient;
} // end divide method
// add method.
public Fraction add(Fraction secondFraction) {
if(denominator != secondFraction.denominator) {
int sumOfDenominators = denominator * secondFraction.denominator;
int newNumeratorOne = numerator * secondFraction.denominator;
int newNumeratorTwo = secondFraction.numerator * denominator;
int sumOfNumerators = newNumeratorOne + newNumeratorTwo;
Fraction sum = new Fraction(sumOfNumerators, sumOfDenominators);
return sum;
} else {
int sumOfNumerators = numerator + secondFraction.numerator;
Fraction sum = new Fraction(sumOfNumerators, denominator);
return sum;
}
} // end add method.
// subtract method.
public Fraction subtract(Fraction secondFraction) {
if(denominator != secondFraction.denominator) {
int differenceOfDenominators = denominator * secondFraction.denominator;
int newNumeratorOne = numerator * secondFraction.denominator;
int newNumeratorTwo = secondFraction.numerator * denominator;
int differenceOfNumerators = newNumeratorOne - newNumeratorTwo;
Fraction difference = new Fraction(differenceOfNumerators, differenceOfDenominators);
return difference;
} else {
int sumOfNumerators = numerator - secondFraction.numerator;
Fraction difference = new Fraction(sumOfNumerators, denominator);
return difference;
}
} // end subtract method.
// reduce method.
public Fraction reduce (Fraction secondFraction) {
int numerator_abs = Math.abs (numerator);
int denominator_abs = Math.abs (denominator);
int min_num = Math.min(numerator_abs, denominator_abs);
Fraction reducedAnswer = new Fraction(numerator_abs, denominator_abs);
for (int i = 1; i <= min_num; i++) {
if (numerator%i == 0 && denominator%i == 0){
i++;
}//end if
}//end for
return reducedAnswer;
}//end reduce
} // end class
答案 0 :(得分：2)
在reduce功能中，你不会改变reducedAnswer，所以你不能减少分数。
另外，你要返回分数的abs值，女巫可能不是你想要的。
BTW - 您可能希望使用https://en.wikipedia.org/wiki/Euclidean_algorithm来查找缩减过程中最大的公约数。
答案 1 :(得分：0)
您可以像这样编写缩小方法
public void reduce ()
{
BigInteger num = BigInteger.valueOf(numerator);
int gcd = num.gcd(BigInteger.valueOf(denominator)).intValue();
this.denominator /= gcd;
this.numerator /= gcd;
}
答案 2 :(得分：0)
您的reduce方法只是在缩减循环之前设置结果，它本身似乎没有效果。鉴于减少纯粹是一个分数特征，它应该是你的分数类的一种方法。此外，Elucid的GCD对计算最大公分母更为有效。鉴于此，我建议如下。
NSTimeZone *tz = [[NSTimeZone timeZoneForSecondsFromGMT:(-8 * 3600)];
[dateFormatter setTimeZone:tz];
NSString* s = [dateFormatter stringFromDate:now];